Consider a pyramid OPQRS located in the first octant (x 0, y 0, z 0) with O as origin, and OP and OR along the x-axis and the y-axis, respectively. The bases OPQR of the pyramid is a square with OP= 3. The point S is directly above the mid-point T of diagonal OQ such that TS = 3. Then (A) the acute angle between OQ and OS is 3 (B) the equation of the plane containing the triangle OQS is x - y = 0 3 (C) the length of the perpendicular from P to the plane containing the triangle OQS is 2 15 (D) the perpendicular distance from O to the straight line containing RS is 2